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Viscoplastic lattice strain during repeated relaxation of age-hardened Al alloy

2021; Elsevier BV; Volume: 158; Linguagem: Inglês

10.1016/j.mechmat.2021.103899

1872-7743

Hyongjoon Lee, Hobyung Chae, You Sub Kim, Min Ji Song, Sangyeob Lim, Kali Prasad, K. Hariharan, Jayant Jain, Ke An, Soo Yeol Lee,

Aluminum Alloy Microstructure Properties

We examined the repetitive stress relaxation behavior of extruded AA7075 subjected to different heat-treatments (solid-solutionized (SS), under-aged (UA), peak-aged (PA)). Compared to SS and UA, the PA showed the highest stress drop (Δσs), plastic strain change (Δεp) and re-yielding (Δσr), in conjunction with the largest reduction in mobile dislocation density right after stress relaxation. As stress relaxation cycles repeated, the stress drop decreased due to lower activities of mobile dislocations. During stress relaxation, the harder the grain orientation was, the more was the reduction in lattice strain. However, this tendency was not consistent with the order in the magnitude of the shear stresses imposed on the respective grains based on Schmid's law. The current results confirm the grain-orientation dependency on the relative activities of dislocation slip and diffusion-controlled creep during the stress relaxation at room temperature.